The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Some internal combustion engines include engine control systems that deactivate one or more cylinders during operation. The deactivation typically occurs under low load situations. For example, an eight cylinder engine can be operated using four cylinders to improve fuel economy by reducing pumping losses. This process is generally referred to as displacement on demand or DOD. Operation using all of the engine cylinders is referred to as an activated mode. A deactivated mode refers to operation using less than all of the cylinders of the engine (one or more cylinders not active).
Conventional methods of controlling the engine to transition between the activated mode and the deactivated mode are based on engine vacuum. Some methods include an engine vacuum hysteresis pair to prevent toggling between the activated and deactivated modes. These methods neglect engine torque and have a negative impact on fuel economy during low engine torque conditions. Likewise, the methods tend to have a negative impact on noise, vibration, and harshness during high engine torque conditions.